Currently available personal direct-reading instruments for organic gases and vapors are limited by the poor selectivity of the sensing components employed. Determination of the concentrations of individual components of even simple mixtures is generally not possible. Thus, there is a need for improvements in sensor technology for industrial hygiene monitoring applications. The development of highly selective chemical microsensors and associated microinstrumentation would greatly improve our ability to characterize and control occupational exposures to toxic chemicals. We propose to develop a compact prototype instrument that utilizes a coated surface-acoustic-wave (SAW) chemical microsensor to achieve selective, real-time measurement of each of the following olefin gases and vapors: acrylonitrile, butadiene, beta-chloroprene, ethylacrylate, styrene, vinyl chloride, and vinylidene chloride. These target olefins were chosen due to their potential carcinogenic, neurotoxic, and/or adverse-reproductive health effects. Selectivity for a given target olefin will be achieved by coating the surface of the SAW device with one of several organoplatinum reagents designed to react specifically with that olefin. Preliminary studies have shown that subtle changes of the ligands in the reagent result in selective reactivity toward certain olefins in the presence of other olefin and non-olefin co-contaminants. Furthermore, following exhaustive exposure the original trapping reagent can be regenerated, in situ, by simple chemical treatment, permitting repeated use of the sensor. A dual 97-MHz SAW.device having an integrated surface heating element and an overall area of 0.8 cm2 will be fabricated in our laboratory. The prototype instrument will be constructed from a single-board computer, modified to accomodat the SAW microsensor and the associated circuitry. The instrument will be equipped with data-storage and digital-readout capabilities for both real-time and timeweighted-average measurements. Instrument performance will be evaluated using dynamic test atmospheres with respect to several relevant operating parameters.